Biomedical Engineering Reference
In-Depth Information
2.1. Datasets description
The equipment used to collect PRB data during this study was the Applied
Science Laboratories (ASL) Model 501 head-mounted optics system. Pupil
size was recorded at a rate of 60 Hz for each participant over 105 trials of
a computer-based task using a graphical user interface (GUI). A camera
records the pupil image, which has been distinguished by a near-infrared
beam that illuminates the interior of the eye. Pupil size is assessed as the
number of pixels attributed to the pupil's image, which has been determined
by real-time edge detection processing of the image. Actual pupil diameter
measurements (in millimeters) are then calculated by multiplying each pixel
value by a scaling factor that is based on the physical distance of the camera
from each participant's eye.
The dataset is comprised of PRB data streams for 36 individuals, as
described in Table 1. In this table, N refers to the number of individuals
comprising this user group. Visual acuity refers to the range of Snellen
visual acuity scores (assessed by ETDRS) of the better eye for participants
of each group. AMD? refers to the presence (Yes) or absence (No) of this
ocular disease in individuals within each group. Number of data sets refers
to the number of 2048-length data sets that were obtained from the data
streams for each group. For this study, data was collected from four groups
of individuals, classied by visual acuity and the presence or absence of
age-related macular degeneration (AMD). Visual acuity, an individual's
ability to resolve ne visual detail, was assessed via the protocol outlined
in the Early Treatment of Diabetic Retinopathy Study (ETDRS) 20 . The
experimental protocol from this study is fully described in studies by Jacko
and colleagues 3;19 .
Table 1.
Group characteristics summary
Group
N
Visual Acuity
AMD?
Number of Data Sets
Control
19
20/20 - 20/40
No
111
#1
6
20/20 - 20/50
Yes
59
#2
5
20/60 - 20/100
Yes
57
#3
6
20/100
Yes
124
2.2. Preprocessing
Studies of PRB are faced with the problem of how to remove blink artifacts.
A blink generally lasts about 70-100 msec. (producing an artifact spanning
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